Amyloid-beta (A-beta), which exists as a 36-43 amino acid peptide, is a product released from amyloid precursor protein (APP) by the enzymes β and γ secretase. In AD patients, A-beta can be present in soluble monomers, insoluble fibrils and soluble oligomers. In monomer form, A-beta exists as a predominantly unstructured polypeptide chain. In fibril form, A-beta can aggregate into distinct morphologies, often referred to as strains. Several of these structures have been determined by solid-state NMR.
For, example, structures for several strains of fibrils are available in the Protein Data Bank (PDB), a crystallographic database of atomic resolution three dimensional structural data, including a 3-fold symmetric Aβ structure (PDB entry, 2M4J); a two-fold symmetric structure of Aβ-40 monomers (PDB entry 2LMN), and a single-chain, parallel in-register structure of Aβ-42 monomers (PDB entry 2MXU).
The structure of 2M4J is reported in Lu et al [8], and the structure of 2MXU is reported in Xiao et al [9]. The structure of 2LMN is reported in Petkova et al [10].
A-beta oligomers have been shown to kill cell lines and neurons in culture and block a critical synaptic activity that subserves memory, referred to as long term potentiation (LTP), in slice cultures and living animals.
The structure of the oligomer has not been determined to date. Moreover, NMR and other evidence indicates that the oligomer exists not in a single well-defined structure, but in a conformationally-plastic, malleable structural ensemble with limited regularity. Moreover, the concentration of toxic oligomer species is far below either that of the monomer or fibril (estimates vary but are on the order of 1000-fold below or more), making this target elusive.
Antibodies that bind A-beta have been described.
WO2009048538A2 titled USE OF ANTI-AMYLOID ANTIBODY IN OCULAR DISEASES discloses chimeric antibodies that recognize one or more binding sites on A-beta and are useful for the treatment for ocular diseases.
U.S. Pat. No. 9,221,812B2 titled COMPOUNDS FOR THE TREATMENT OF DISEASES ASSOCIATED WITH AMYLOID OR AMYLOID-LIKE PROTEINS describes pharmaceutical compositions and discontinuous antibodies that bind A-beta including an epitope between amino acid residues 12 to 24 for the treatment of amyloid-related diseases.
WO2003070760A2 titled ANTI-AMYLOID BETA ANTIBODIES AND THEIR USE discloses antibodies that recognize an A-beta discontinuous epitope, wherein the first region comprises the amino acid sequence AEFRHDSGY or a fragment thereof and wherein the second region comprises the amino acid sequence VHHQKLVFFAEDVG or a fragment thereof.
US20110171243A1 titled COMPOUNDS TREATING AMYLOIDOSES discloses a peptide mimotope capable of inducing the in vivo formation of antibodies that bind HQKLVF and/or HQKLVFFAED, and its use.
WO2008088983A1 and WO2001062801A2 disclose a pegylated antibody fragment that binds A-beta amino acids 13-28 (HHQKLVFFAEDVGSNK) and its use in treating A-beta related diseases.
WO2009149487A2 titled COMPOUNDS FOR TREATING SYMPTOMS ASSOCIATED WITH PARKINSON'S DISEASE describes compounds comprising a peptide having binding capacity for an antibody specific for an A-beta epitope such as EVHHQKL, HQKLVF and HQKLVFFAED.
The HHQK (SEQ ID NO: 1) domain is described as involved in plaque induction of neurotoxicity in human microglia, as described in Giulian D et al. [11] and Winkler et al. [12]. Non-antibody therapeutic agents that bind HHQK (SEQ ID NO: 1) have been disclosed for the treatment of protein folding diseases (US20150105344A1, WO2006125324A1).
WO2010128139A1 titled BIOMARKERS AND METHODS FOR DIAGNOSING ALZHEIMER'S DISEASE AND/OR MILD COGNITIVE IMPAIRMENT discloses a diagnostic method for Alzheimer's disease through assessing levels of antibodies capable of binding pGlu A-Beta in a given subject's body fluid.
WO2011033046A1 titled NOVEL ASSAY FOR THE DETECTION OF AMYLOID BETA PEPTIDES discloses a method for detection of A-beta (1-40).
WO2014161875A1 titled METHOD FOR DETECTING Aβ-SPECIFIC ANTIBODIES IN A BIOLOGICAL SAMPLE discloses a method for detecting A-beta-specific antibodies using A-beta variants for the diagnosis of Alzheimer's disease.
U.S. Pat. Nos. 5,766,846; 5,837,672; and 5,593,846 (which are incorporated herein by reference) describe the production of murine monoclonal antibodies to the central domain of the Aβ peptide. WO 01/62801 describes antibodies that bind A-beta between amino acids 13-28. WO2004071408 discloses humanized antibodies. WO2008088983A1 describes an antibody fragment that binds amyloid beta (A-beta) peptide and is covalently attached to one or more molecules of polyethylene glycol (PEG), the antibody fragment specifically binding human A-beta peptide between amino acid positions 13-28. Solanezumab and Crenezumab bind amino acids 16-26 on A-beta. Crenezumab interacts with the monomer, oligomer and fibril. Midregion antibodies, including solanezumab (picomolar affinity) and crenezumab (nanomolar affinity), appear to preferentially bind monomeric A-beta [16].
Antibodies that preferentially or selectively bind A-beta oligomers and inhibit A-beta oligomerization are desirable for therapeutic intervention.